THIS isn't about props as mere pegs to hang acting on: the bunch of grapes to peck at, the specs to twiddle. Good props grab our attention the moment we see them, reappear throughout the play and reveal something new each time. Otway's dagger does all this and more; it even takes centre-stage for the climactic Liebestod.

Bafflingly, though, its journey from hand to hand doesn't add up. Characters produce it who seem never to have been given it in the first place. A startling continuity-jump has the febrile hero, Jaffeir, throwing it to the ground (Kean's big moment) and exiting grandly, only to bring it back on with him next time he enters. Otway isn't bothered about getting the dagger from A to B. What interests him is that it is male and sexual.

Bedamar and his cronies are plotting to overthrow the state of Venice. Otway connects the attempt with violent sex: 'How lovely the Adriatic whore, dressed in her flames, will shine]' A new concept for Jaffeir, till now a mild and attentive husband.

Moments later, we see him handing over both his dagger and his wife Belvidera to the conspirators; it's the familiar sight of a man in the grip of an obsession throwing away everything which stands for his life so far. Free to follow his instinct, he turns to the man who involved him in the conspiracy in the first place, and fervently (if unconsciously) woos him:

Oh Pierre, wert thou but she,

How I could pull thee down into my heart,

Gaze on thee till my eye-strings cracked with love,

Till all my sinews with its fire extended,

Fixed me upon the rack of ardent longing;

Then swelling, sighing, raging to be blest,

Come like a panting turtle to thy breast . . .

The dagger stays out of sight for the next few scenes, but it is still a lively presence, even getting involved in an attempted off-stage rape. Act Four has it back on stage in a series of grand encounters of love and rejection.

Jaffeir has exposed the conspiracy. Pierre, captured and in chains, hits him. Jaffeir is disappointed. 'Had not a dagger done thee nobler justice?', he complains. But in fierce rejection Pierre gives the dagger back to him, and from now on, Jaffeir wears it sensuously inside his shirt, 'where it may grow acquainted with my heart'. What he cannot forgive is Belvidera's role in the break- up with Pierre. He keeps nearly stabbing her but never quite makes it. She - as jilted partners so often do - will settle for penetration on any terms:

and when thy hands

Charg'd with my fate, come trembling to the deed,

As thou hast done a thousand thousand dear times,

To this poor breast, when kinder rage has brought thee,

When our stinged hearts have leaped to meet each other,

And melting kisses sealed our lips together,

When joys have left me gasping in thy arms,

So let my death come now, and I'll not shrink from't.

Too late. He's speeding into the wings, weapon in hand. 'Leave thy dagger with me,' she implores. But she's lost him: Pierre is waiting on the executioner's scaffold, erotically poised for torture and execution. Jaffeir stabs both Pierre and himself, and with his dying words bequeaths the primal weapon to Belvidera.

But sex, in Venice Preserv'd, is something which happens between men or (as we see in the lively subplot, featuring another dagger) between a man and a whore. So Belvidera is never given the dagger: she simply dies. The lovers' union beyond the grave is signalled by an unusual joint appearance: 'The ghosts of Jaffeir and Pierre rise together, both bloody.'

Without the prop, the homosexual subtext would go unnoticed. Even with it, it's often downplayed: I don't think Garrick or Kean made much of it. But it was spotted by Balzac, whose homosexual master-criminal Vautrin introduces it into the conversation at exactly the point where gay seducers a century later would bring out a well-thumbed copy of Giovanni's Room:

'My child', said the Spaniard, taking Lucien by the arm, 'Have you pondered over Otway's Venice Preserved? Have you understood the deep friendship between man and man which binds Pierre to Jaffeir, makes them indifferent about women and alters all social relationships for them? I'm putting that question to the poet in you.'